1. Field of the Invention
The present invention relates to a bar code reading technology, and in particular, to that suitable in an environment that a bar code that contains a supplemental portion and a bar code that does not contain a supplemental portion coexist.
2. Description of the Related Art
Bar codes that are combinations of white vertical lines and black vertical lines have been widely used to represent commodity information and so forth. A conventional bar code is composed of only a main portion 501 as shown in FIG. 1. However, for some commodity information, a bar code that contains a supplemental portion 602 along with a main portion 601 as shown in FIG. 2 is used. Thus, under an environment that such two types of bar codes coexist, a bar code reading apparatus that can read both bar codes that contain a supplemental portion and bar codes that do not contain a supplemental portion is required.
To allow both bar codes that contain a supplemental portion and bar codes that do not contain a supplemental portion to be read, a process for recognizing whether or not a bar code contains a supplemental portion is required. In other words, since a main portion of a bar code which also contains a supplemental portion can be treated as an independent bar code, if the above process of recognizing is not performed, the bar code reading process is completed after only the main portion is scanned and decoded. Thus, the supplemental portion may not be read and decoded. For example, if an operator handles a bar code render so that the bar code reader scans only a main portion of a bar code which also has a supplemental portion as shown in FIG. 3, the bar code reading process is completed after only the main portion is scanned and decoded.
As a related art reference, Japanese Patent Laid-Open Publication No. 8-329175 discloses a bar code reading apparatus.
The related art reference describes the following two types of bar code reading apparatuses. In the first bar code reading apparatus, when a main portion of a bar code is decoded unless a supplemental portion is not decoded, a timer is started. If the supplemental portion is decoded in a predetermined time period after the timer has been started, the decoded results of both the main portion and the supplemental portion are output. In contrast, when the supplemental portion is not decoded in the predetermined time period after the timer has been started, the decoded result of only the main portion is output. In other words, in the first bar code reading apparatus, an extension time period necessary for detecting whether or not the supplemental portion exists is generated by the timer process. In the extension time period, it is recognized whether or not the supplemental portion exists so as to prevent the supplemental portion from being dropped.
On the other hand, in the second bar code reading apparatus described in the forgoing related art reference, it is recognized whether or not a bar code contains a supplemental portion depending on whether or not the first three digits of the main portion are one of xe2x80x9c977xe2x80x9d and xe2x80x9c978xe2x80x9d. If the first three digits are one of xe2x80x9c977xe2x80x9d and xe2x80x9c978xe2x80x9d, that is, if the recognized result represents that the bar code contains a supplemental portion, then the decoded result is prohibited from being transferred to a host unit until the supplemental portion has been decoded. On the other hand, if the recognized result represents that the bar code does not contain a supplemental portion, the decoded result of only the main portion is transferred to the host unit.
However, the forgoing first and second bar code reading apparatuses (hereinafter that are referred to as first related art technology and second related art technology, respectively) have the following disadvantages.
 less than Disadvantages of First Related Art Technology greater than 
As a first disadvantage of the first related art technology, since the extension time is required to detect a supplemental portion, even a bar code that does not contain a supplemental portion is always read with the extension time.
As a second disadvantage, most stores use bar codes that do not contain a supplemental portion. These stores use bar codes that contain a supplemental portion in an exceptional case. Thus, when a bar code reading apparatus reads a bar code that does not contain a supplemental portion with such a delay time, it adversely affects the their business operations.
As a third disadvantage, if the extension time period necessary for detecting a supplemental portion is shortened, the reading speed of a bar code that does not contain a supplemental portion can be improved. However, the drop ratio of a supplemental portion of a bar code becomes high. As a result, the bar code reading apparatus cannot be practically used.
 less than Disadvantage of Second Related Art Technology greater than 
In the second related art technology, it is recognized whether or not a bar code contains a supplemental portion depending on whether or not the first three digits of a main portion of the bar code is one of xe2x80x9c977xe2x80x9d and xe2x80x9c978xe2x80x9d. Thus, the reading speed of the second related art technology is higher than that of the first bar code reading apparatus. However, according to the second related art technology, if the first three digits of a main portion of a bar code is one of xe2x80x9c977xe2x80x9d and xe2x80x9c978xe2x80x9d, the decoded result is prohibited from being transferred to the host unit until the decoded result of the supplemental portion is obtained. Thus, if the supplemental portion cannot be decoded due to a dirt or a drop, the process is delayed for a long time
Therefore, an object of the present invention is to allow the reading speed of a bar code to be improved in an environment that a bar code that contains a supplemental portion and a bar code that does not contain a supplemental portion coexist and to prevent the reading process from being delayed for a long time if the supplemental portion is expected to be read but cannot be read due to a dirt, a drop, or the like.
According to the present invention, there is provided a bar code reading method, comprising the steps of: performing a supplemental portion presence/absence determining process for determining whether or not a bar code contains a supplemental portion depending on whether or not an analyzed result of a predetermined number of digits starting from a predetermined digit position in a main portion of the bar code matches a predetermined code; if the determined result of the supplemental portion presence/absence determining process represents that the bar code does not contain the supplemental portion, outputting the analyzed result of the main portion; if the determined result of the supplemental portion presence/absence determining process represents that the bar code contains the supplemental portion, performing an analyzing process for the supplemental portion until the analyzed result of the supplemental portion is obtained or until a predetermined time period elapses; if the analyzed result has not been obtained when the predetermined time period elapses, outputting the analyzed result of only the main portion; and if the analyzed result of the supplemental portion has been obtained before the predetermined time period elapses, combining the analyzed result of the main portion and the analyzed result of the supplemental portion and outputting the combined result.
The bar code reading method may further comprises the steps of: before the supplemental portion presence/absence determining process is performed, determining whether or not the bar code is a type of bar code which has a possibility that the bar code contains a supplemental portion; and if the bar code is not the type of bar code, outputting the analyzed result of the only main portion without performing the supplemental portion presence/absence determining process; and if the bar code is the type of bar code, performing the supplemental portion presence/absence determining process.
In the bar code reading method, the type of a bar code which has the possibility that the bar code contains a supplemental portion may be one of EAN-13, EAN-8, UPC-A, and UPC-E.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of the best mode embodiment thereof, as illustrated in the accompanying drawings.